The invention relates to ECG recorders, and in particular to recorders adapted to be used by a patient to record his or her own cardiac activity.
It has been found that in patients suffering from intermittent occurrences of abnormal cardiac acitivity it is difficult to obtain a recording of the elecrocardiogram of the abnormal activity because of the uncertainty as to when this will occur. For example, a patient may feel symptoms which recur at unpredictable times and at intervals of several days or more. It is desirable to examine the electrocardiogram during these symptoms for diagnostic purposes. It is of course possible to arrange for the patient to stay in hospital and be permanently connected to a cardiac monitoring apparatus. However, this is expensive and there is no guarantee that the symptoms will recur within a reasonable time. Further, a considerable amount of data will be collected which contains no useful information and it is very time consuming and expensive to scan long periods of a normal ECG whilst searching for abnormal activity. A further disadvantage of long-term monitoring is that the patient electrode contact deteriorates and has to be renewed to avoid poor results.
Ambulatory monitors have been proposed, e.g. the so-called "24 hour monitor". Although these are less expensive to use than the cost of hospital monitoring, they have the same disadvantages associated with long-term monitoring. An ambulatory monitor has been described which employs chest electrodes which the patient is expected to apply when feeling symptoms. However, relatively involved procedures have to be followed to apply the electrodes and start the recorder, and the patient may fail to follow the procedures correctly or may not be able to carry out the procedures before the symptoms vanish. Means have to be provided in the monitor to indicate the correct connection of the electrode and proper operation of the recorder.
To facilitate setting up of the system by the patient it is desirable that the electrode arrangement should be as simple as possible, and should permit easy application by the patient. Hitherto, electrode arrangements for cardiac monitoring have comprised one or more electrodes which are applied to the patient's chest, e.g. by adhesive tape. The application of such electrodes requires the patient to partially undress, and in order to ensure good adhesion and good contact the area to which the electrodes are to be applied must be shaved and swabbed using surgical spirit or similar. The application of such electrodes takes time, during which relevant information may be lost, and also provides opportunity for patient error.